This invention concerns a rotary resistor or rheostat. It particularly relates to very small rotary resistors the preferred field of application of which is in hearing aids worn behind the ear. These hearing aids are carried behind the ear and in view of the space available, must be very small. The invention concerns in particular rotary resistors consisting of a substrate with layers of precious metals, nonprecious metals, metal oxides or other materials forming conductors or resistances applied to it.
The electric connection between the wiper potential and the rear solder contact surface consists in these rotary resistors of a pin or rivet forming the rotating axle of the wiper. Both of these embodiments have the disadvantage that especially in very small configurations the manufacture and the mounting of the rivet or the pin is extraordinarily difficult and thus expensive. Furthermore, the transfer resistances between the rivet or the pin and the rear solder contact surface and the wiper are relatively high.
It is known according to German Publication No. DE-GM 72 76 541, in a variable resistor with a support base and a resistance and wiper path, asymmetrically to said path a plurality of boreholes is provided, connected at their ends by conductors, which, however, as the result of their position serve an entirely different purpose, i.e., the additional fastening of the conductors and possibly the creation of further potential connections. In the case of the invention, on the other hand, the metal coating serves to conduct the wiper potential to the rear solder contact surface without difficulty and with the least possible transfer resistance.